Fuel tank thread

Can anyone please tell me the size of the thread on a lister d fuel tank . the reducer with filter attached that actually fits into the tank and then you add your 1/4 threaded tap to . I now see you can get a new tap with modern filter attached fairly reasonable priced unlike a lister tap with filter combined even bashed and leaking are going for silly money  , But the new ones are male/male 1/4 threaded filter attached to the tap so you would need to get an adapter to screw into the tank , then fit it .